CSLB General Building (B) — All Questions

A technician measures the distance from the beginning of the P wave to the beginning of the QRS complex on a strip and counts four small boxes. What is the PR interval, and is it normal?

• a.0.04 second, which is shorter than normal
• b.0.08 second, which is normal
• c.0.16 second, which is normal✓
• d.0.40 second, which is longer than normal

Each small box equals 0.04 second at the standard paper speed of 25 mm/sec, so four small boxes equal 0.16 second. The normal PR interval is 0.12 to 0.20 second, so 0.16 second falls in range. The 0.04 and 0.08 answers miscount the boxes, and 0.40 second would require ten small boxes and would indicate a first-degree AV block.

What is the normal duration of the QRS complex in an adult?

• a.Less than 0.12 second✓
• b.0.12 to 0.20 second
• c.0.20 to 0.36 second
• d.Greater than 0.44 second

A normal QRS is under 0.12 second (fewer than three small boxes) because the ventricles depolarize rapidly through the bundle branches and Purkinje fibers. The 0.12 to 0.20 second range describes the PR interval, not the QRS. Values of 0.20 second or more suggest a bundle branch block or a beat that started in the ventricles, and 0.44 second is a QT-interval reference, not a QRS value.

Using the 300 method on a regular rhythm, a technician counts four large boxes between two consecutive R waves. What is the heart rate?

• a.60 beats per minute
• b.75 beats per minute✓
• c.100 beats per minute
• d.150 beats per minute

The 300 method divides 300 by the number of large boxes between R waves, so 300 divided by 4 equals 75 beats per minute. Sixty would require five large boxes, 100 would require three, and 150 would require two. The method only works when the rhythm is regular, because it assumes every R-R interval is the same.

A patient has an irregular rhythm. The technician counts 11 QRS complexes in a six-second strip. What is the approximate heart rate?

• a.11 beats per minute
• b.22 beats per minute
• c.66 beats per minute
• d.110 beats per minute✓

The six-second method multiplies the number of QRS complexes in six seconds by 10, giving 11 times 10, or about 110 beats per minute. This estimate is the preferred method for irregular rhythms because the 300 and 1500 methods assume equal R-R intervals. Multiplying by 2 or 6 instead of 10 gives the wrong scaling, since six seconds is one tenth of a minute.

What electrical event does the P wave represent on an EKG tracing?

• a.Ventricular repolarization
• b.Ventricular depolarization
• c.Atrial depolarization✓
• d.Atrial repolarization

The P wave is the small rounded deflection produced when the impulse from the SA node spreads across both atria and depolarizes them, which triggers atrial contraction. Ventricular depolarization produces the QRS complex, and ventricular repolarization produces the T wave. Atrial repolarization does occur, but it is buried inside the much larger QRS complex and is not normally visible.

A technician is explaining a tracing to a student and points to the rounded wave that follows each QRS complex. What does this wave represent?

• a.Repolarization of the ventricles✓
• b.Depolarization of the ventricles
• c.Conduction delay at the AV node
• d.Contraction of the atria

The T wave follows the QRS and represents ventricular repolarization, the recovery phase in which the ventricular cells return to their resting electrical state. Ventricular depolarization is the QRS itself. The AV node delay is represented by the flat segment within the PR interval, and atrial contraction follows the P wave.

Using the 1500 method, a technician counts 20 small boxes between two consecutive R waves on a regular strip. What is the heart rate?

• a.50 beats per minute
• b.75 beats per minute✓
• c.100 beats per minute
• d.300 beats per minute

The 1500 method divides 1500 by the number of small boxes between R waves: 1500 divided by 20 equals 75 beats per minute. The number 1500 is used because there are 1500 small boxes in one minute at 25 mm/sec. This method is the most precise of the calculation methods, but like the 300 method it requires a regular rhythm.

Which set of findings meets the criteria for normal sinus rhythm?

• a.Rate 110, regular, one upright P wave per QRS, PR 0.16 second
• b.Rate 80, irregular, P waves absent, QRS 0.08 second
• c.Rate 50, regular, inverted P waves, PR 0.10 second
• d.Rate 80, regular, one upright P wave before every QRS, PR 0.16 second, QRS 0.08 second✓

Normal sinus rhythm requires a rate of 60 to 100, a regular rhythm, one upright P wave in front of every QRS, a PR interval of 0.12 to 0.20 second, and a QRS under 0.12 second. A rate of 110 is sinus tachycardia, absent P waves with an irregular rhythm suggests atrial fibrillation, and a rate of 50 with inverted P waves and a short PR points to a junctional rhythm.

A sleeping athlete on telemetry shows a regular rhythm at 52 beats per minute with an upright P wave before each narrow QRS and a PR interval of 0.16 second. How should this rhythm be identified?

• a.Normal sinus rhythm
• b.Junctional escape rhythm
• c.Sinus bradycardia✓
• d.Second-degree AV block

Every measurement is normal except the rate, which is below 60, so the rhythm is sinus bradycardia. Normal sinus rhythm requires a rate of at least 60. A junctional escape rhythm would show absent or inverted P waves, and a second-degree AV block would show P waves that are not all followed by a QRS complex.

A patient with a fever of 103 degrees Fahrenheit has a regular rhythm at 124 beats per minute with an upright P wave before every narrow QRS. What is this rhythm?

• a.Sinus tachycardia✓
• b.Supraventricular tachycardia
• c.Atrial flutter
• d.Ventricular tachycardia

Sinus tachycardia is a sinus rhythm faster than 100 beats per minute, and it is a normal response to fever, pain, exercise, anxiety, or dehydration. Supraventricular tachycardia is usually faster than 150 and the P waves are hidden. Atrial flutter shows sawtooth flutter waves, and ventricular tachycardia produces wide QRS complexes with no P waves.

A pediatric strip shows upright P waves before every narrow QRS, a PR interval of 0.14 second, and R-R intervals that shorten with inhalation and lengthen with exhalation. What is this rhythm?

• a.Atrial fibrillation
• b.Sinus arrhythmia✓
• c.Wandering atrial pacemaker
• d.Second-degree AV block, Mobitz I

Sinus arrhythmia is a sinus rhythm whose only abnormality is an irregularity that varies with the breathing cycle, and it is a normal finding in children and young adults. Atrial fibrillation would have no identifiable P waves and an irregularly irregular rhythm. Wandering atrial pacemaker shows at least three different P wave shapes, and Mobitz I shows progressively lengthening PR intervals with a dropped QRS.

A strip shows no identifiable P waves, a wavy chaotic baseline, narrow QRS complexes, and R-R intervals that vary from beat to beat with no pattern. What is this rhythm?

• a.Sinus arrhythmia
• b.Atrial flutter
• c.Ventricular fibrillation
• d.Atrial fibrillation✓

Atrial fibrillation is described as irregularly irregular with no discernible P waves and a fibrillatory baseline, while the QRS stays narrow because conduction below the AV node is normal. Sinus arrhythmia still has clear P waves. Atrial flutter has organized sawtooth waves, and ventricular fibrillation has no QRS complexes at all.

A monitor strip shows a sawtooth baseline with regular atrial waves at about 300 per minute and a QRS after every fourth sawtooth wave. What is this rhythm?

• a.Atrial fibrillation
• b.Sinus tachycardia with artifact
• c.Atrial flutter with 4:1 conduction✓
• d.Third-degree AV block

Atrial flutter produces uniform sawtooth flutter waves, classically at 250 to 350 per minute, and the AV node blocks most of them so that only every second, third, or fourth impulse reaches the ventricles. Atrial fibrillation has a chaotic rather than uniform baseline. Sinus tachycardia has discrete P waves, and third-degree block shows normal P waves that are completely unrelated to the QRS complexes.

An otherwise regular sinus strip contains one early beat with a P wave shaped differently from the others, followed by a normal narrow QRS and then a pause. What is the early beat?

• a.Premature atrial contraction✓
• b.Premature ventricular contraction
• c.Premature junctional contraction
• d.Escape beat

A premature atrial contraction arrives early and comes from an irritable site in the atria, so its P wave looks different from the sinus P waves but the QRS remains narrow because conduction to the ventricles is normal. A premature ventricular contraction would be wide and bizarre with no P wave. A junctional premature beat has an inverted or absent P wave, and an escape beat arrives late rather than early.

A patient reports sudden palpitations. The strip shows a perfectly regular narrow-complex rhythm at 180 beats per minute with P waves that cannot be identified. What is the most likely rhythm?

• a.Sinus tachycardia
• b.Supraventricular tachycardia✓
• c.Ventricular tachycardia
• d.Accelerated junctional rhythm

Supraventricular tachycardia is a regular narrow-complex rhythm, usually 150 to 250 beats per minute, in which the P waves are buried in the preceding T waves and cannot be seen. Sinus tachycardia usually stays under 160 and has visible P waves that speed up gradually. Ventricular tachycardia has wide QRS complexes, and an accelerated junctional rhythm runs about 60 to 100.

A strip shows a regular rhythm at 45 beats per minute with narrow QRS complexes and inverted P waves appearing immediately after each QRS. What is this rhythm?

• a.Sinus bradycardia
• b.Idioventricular rhythm
• c.First-degree AV block
• d.Junctional escape rhythm✓

When the junction takes over as pacemaker, the atria depolarize backward, so the P wave is inverted and may fall before, during, or after the QRS; at 40 to 60 beats per minute this is a junctional escape rhythm. Sinus bradycardia has upright P waves before the QRS. An idioventricular rhythm has wide QRS complexes at 20 to 40, and first-degree AV block has upright P waves with a long PR interval.

What is the inherent rate range of the AV junction when it functions as the heart's pacemaker?

• a.100 to 150 beats per minute
• b.60 to 100 beats per minute
• c.40 to 60 beats per minute✓
• d.20 to 40 beats per minute

The AV junction fires at an inherent rate of 40 to 60 beats per minute and takes over when the SA node fails or slows. The SA node is the primary pacemaker at 60 to 100, and the ventricular Purkinje network is the last-resort pacemaker at 20 to 40. A junctional rhythm faster than 60 is called accelerated junctional, and above 100 it is junctional tachycardia.

A sinus rhythm strip contains a single early beat that is wide and bizarre, has no preceding P wave, and has a T wave that points opposite to the QRS. What is the beat?

• a.Premature ventricular contraction✓
• b.Premature atrial contraction
• c.Paced beat
• d.Artifact

A premature ventricular contraction originates below the bundle of His, so the impulse travels cell to cell rather than through the fast conduction system, producing a wide bizarre QRS with no preceding P wave and opposite T wave polarity. A premature atrial contraction stays narrow. A paced beat is preceded by a sharp pacer spike, and artifact does not interrupt the underlying R-R cycle in this way.

A monitor alarms and the strip shows a regular wide-complex rhythm at 170 beats per minute with no visible P waves. The patient is unresponsive. What rhythm is displayed?

• a.Supraventricular tachycardia
• b.Ventricular tachycardia✓
• c.Atrial flutter
• d.Sinus tachycardia with a bundle branch block

Ventricular tachycardia is three or more consecutive PVCs at a rate above 100, appearing as a regular run of wide, uniform complexes without P waves, and it is a lethal rhythm when the patient has no pulse. Supraventricular tachycardia is narrow. Atrial flutter shows sawtooth waves, and while a rate-related bundle branch block can widen a sinus tachycardia, an unresponsive patient with this tracing must be treated as ventricular tachycardia and help summoned at once.

A telemetry strip suddenly shows chaotic, irregular waves of varying height with no identifiable P waves, QRS complexes, or T waves. What should the technician do first?

• a.Reposition the electrodes and print a new strip
• b.Chart the finding and continue monitoring
• c.Ask the patient to lie still and stop talking
• d.Immediately check the patient and call for emergency help✓

That description is ventricular fibrillation, a lethal rhythm in which the ventricles quiver and produce no cardiac output, so the technician must verify the patient at the bedside and activate the emergency response without delay. Documenting and waiting wastes the minutes that determine survival. Repositioning electrodes or asking the patient to hold still is the response to suspected artifact, and artifact is ruled out the moment the patient is found unresponsive and pulseless.

A monitor shows a nearly flat line with no waveforms in two different leads and the patient is unresponsive with no pulse. What is this rhythm?

• a.Ventricular fibrillation
• b.Idioventricular rhythm
• c.Asystole✓
• d.Loose lead artifact

Asystole is the absence of all electrical activity, appearing as a flat or nearly flat line, and it must be confirmed in more than one lead before it is accepted as true. Ventricular fibrillation still shows chaotic deflections, and an idioventricular rhythm shows wide slow complexes. A loose lead can mimic a flat line, which is exactly why the finding is confirmed in a second lead and at the bedside.

A strip shows wide QRS complexes at a regular rate of 32 beats per minute with no P waves. What is this rhythm called?

• a.Idioventricular rhythm✓
• b.Junctional escape rhythm
• c.Sinus bradycardia
• d.Agonal artifact

When the ventricles become the pacemaker of last resort, they fire at their inherent rate of 20 to 40 beats per minute and produce wide complexes without P waves, which is an idioventricular rhythm. A junctional escape rhythm runs 40 to 60 with narrow complexes. Sinus bradycardia has upright P waves and narrow QRS complexes, and this tracing is an organized rhythm rather than artifact.

A regular strip at 68 beats per minute has one upright P wave before every narrow QRS, and every PR interval measures 0.28 second. What is this rhythm?

• a.Normal sinus rhythm
• b.Sinus rhythm with a first-degree AV block✓
• c.Second-degree AV block, Mobitz II
• d.Third-degree AV block

A PR interval that is constant but longer than 0.20 second defines first-degree AV block, in which every impulse still reaches the ventricles but is delayed. Normal sinus rhythm requires a PR of 0.12 to 0.20 second. Mobitz II drops beats without lengthening the PR, and third-degree block shows no consistent relationship between P waves and QRS complexes at all.

A strip shows PR intervals of 0.18, 0.24, 0.32 second, then a P wave with no QRS after it, and the pattern repeats. What is this rhythm?

• a.First-degree AV block
• b.Second-degree AV block, Mobitz II
• c.Third-degree AV block
• d.Second-degree AV block, Mobitz I (Wenckebach)✓

Mobitz I, also called Wenckebach, shows the PR interval getting progressively longer until one P wave is not conducted and a QRS is dropped, then the cycle starts over. First-degree block never drops a beat. Mobitz II drops beats while the conducted PR intervals stay constant, and third-degree block has P waves and QRS complexes that march independently.

A strip shows a constant PR interval of 0.20 second on conducted beats, but every third P wave is suddenly not followed by a QRS complex. What is this rhythm?

• a.Second-degree AV block, Mobitz I
• b.Sinus arrhythmia
• c.Second-degree AV block, Mobitz II✓
• d.Premature atrial contractions that are not conducted

Mobitz II is identified by dropped QRS complexes with no warning and PR intervals that remain constant on the beats that do conduct. Mobitz I would show the PR lengthening before the drop. Sinus arrhythmia never drops a QRS, and non-conducted premature atrial contractions arrive early with abnormal P waves rather than on schedule.

A strip shows a regular ventricular rhythm at 40 beats per minute with wide QRS complexes, regular P waves at 80 per minute, and no consistent relationship between the P waves and the QRS complexes. What is this rhythm?

• a.Second-degree AV block, Mobitz I
• b.Third-degree (complete) AV block✓
• c.Sinus bradycardia with premature atrial contractions
• d.Junctional escape rhythm

In third-degree AV block nothing crosses the AV node, so the atria and ventricles beat independently: the P-P interval is regular, the R-R interval is regular, and the PR interval constantly changes. Mobitz I still conducts most beats with a lengthening PR. Sinus bradycardia keeps one P wave tied to each QRS, and a pure junctional escape rhythm would not show a separate faster atrial rate marching through the tracing.

A strip shows a sharp, narrow vertical spike immediately before each wide QRS complex at a regular rate of 70. What does this indicate?

• a.A ventricular paced rhythm✓
• b.Sixty-cycle AC interference
• c.A premature ventricular contraction pattern
• d.Somatic tremor artifact

A pacemaker spike is a thin vertical line marking the electrical impulse delivered by the device; a spike followed by a wide QRS indicates ventricular capture. AC interference appears as a uniform fuzzy band across the whole tracing rather than a single spike per beat. Premature ventricular contractions occur early and irregularly without spikes, and somatic tremor causes erratic jagged baseline movement.

A monitor alarms for ventricular fibrillation, but the technician finds the patient sitting up, alert, and brushing her teeth, and a regular narrow-complex rhythm is visible between the chaotic sections. What is the most likely explanation?

• a.Intermittent true ventricular fibrillation
• b.Third-degree AV block
• c.Pacemaker malfunction
• d.Muscle movement artifact✓

An alert, talking patient cannot be in ventricular fibrillation, and the presence of underlying normal complexes marching through the chaos identifies the tracing as motion artifact. True ventricular fibrillation has no organized QRS complexes anywhere and produces immediate unresponsiveness. AV block and pacemaker failure both produce organized, measurable patterns rather than chaotic noise tied to the patient's activity.

Which group of rhythms is considered immediately life-threatening and requires the technician to summon help right away?

• a.Sinus bradycardia, sinus tachycardia, and sinus arrhythmia
• b.First-degree AV block, atrial flutter, and premature atrial contractions
• c.Ventricular fibrillation, pulseless ventricular tachycardia, and asystole✓
• d.Junctional rhythm, wandering atrial pacemaker, and paced rhythm

Ventricular fibrillation, pulseless ventricular tachycardia, and asystole produce no effective cardiac output, so survival depends on immediate recognition and activation of the emergency response. The sinus rhythms in the first choice are common and often benign. First-degree block, flutter, and premature atrial beats need reporting but not emergency action, and junctional or paced rhythms usually maintain perfusion.

What does the QT interval measure on an EKG tracing?

• a.The time for the atria to depolarize and repolarize
• b.The total time for ventricular depolarization and repolarization✓
• c.The delay of the impulse at the AV node
• d.The time between two consecutive R waves

The QT interval is measured from the start of the QRS complex to the end of the T wave and represents the full cycle of ventricular depolarization and recovery; it normally occupies less than half of the R-R interval and generally measures under about 0.44 second at normal rates. Atrial activity is represented by the P wave. The AV nodal delay lies inside the PR interval, and the R-R interval measures rate and regularity.

A strip shows a normal sinus beat followed by a wide bizarre beat, then another sinus beat followed by another wide bizarre beat, repeating throughout the strip. What is this pattern called?

• a.Ventricular bigeminy✓
• b.Ventricular trigeminy
• c.A couplet
• d.Ventricular tachycardia

Bigeminy means every other beat is a premature ventricular contraction, alternating one normal beat and one PVC. Trigeminy is a PVC every third beat. A couplet is two PVCs in a row, and three or more consecutive PVCs at a rate above 100 constitute ventricular tachycardia.

Which premature ventricular contraction pattern is considered most dangerous because it can trigger ventricular tachycardia or fibrillation?

• a.A unifocal PVC that is late in the cycle
• b.An interpolated PVC between two normal beats
• c.A PVC followed by a full compensatory pause
• d.A PVC that lands on the T wave of the preceding beat✓

A PVC falling on the T wave, called the R-on-T phenomenon, arrives during the vulnerable relative refractory period of repolarization and can precipitate ventricular tachycardia or fibrillation. Unifocal PVCs that arrive later in the cycle are the least worrisome type. An interpolated PVC does not disturb the underlying rhythm, and a compensatory pause is a normal feature of most PVCs rather than a warning sign.

An otherwise normal sinus strip contains one early narrow beat with an inverted P wave right in front of it and a PR interval of 0.08 second. What is this beat?

• a.Premature atrial contraction
• b.Premature ventricular contraction
• c.Premature junctional contraction✓
• d.Sinus escape beat

A premature junctional contraction comes from the AV junction, so the atria depolarize retrograde and produce an inverted P wave with a short PR of less than 0.12 second, while the QRS stays narrow. A premature atrial contraction has an upright though differently shaped P wave with a normal PR. A PVC is wide with no P wave, and an escape beat comes late, not early.

What is the correct way to determine whether a ventricular rhythm is regular?

• a.Compare the height of each R wave across the strip
• b.Measure the R-to-R intervals across the strip and see whether they are equal✓
• c.Count the number of P waves in six seconds
• d.Compare each PR interval to 0.20 second

Ventricular regularity is judged by marching out the R-to-R intervals with calipers or paper and checking whether they stay the same; atrial regularity is judged the same way using P-to-P intervals. R wave height reflects voltage and lead placement, not regularity. Counting P waves gives the atrial rate, and measuring PR intervals evaluates AV conduction.

On standard EKG paper running at 25 mm/sec, how far apart are the vertical time markers printed at the top of the strip used for the six-second method?

• a.Three seconds apart, so two intervals equal six seconds✓
• b.One second apart, so six intervals equal six seconds
• c.Six seconds apart, so one interval equals six seconds
• d.Half a second apart, so twelve intervals equal six seconds

EKG paper is marked at three-second intervals, which equals 15 large boxes, so a six-second strip spans two marked intervals or 30 large boxes. Each large box is 0.20 second and each small box is 0.04 second at the standard 25 mm/sec speed. The other spacings do not correspond to how standard EKG paper is printed.